Imaging Apparatus Tilt Control for Depth of Field
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Solution Overview
Problem
Conventional surveillance cameras with obliquely directed optical axes face challenges in maintaining focus across varying depths in an imaging scene, leading to out-of-focus areas due to mismatched focal and imaging planes, and existing tilt control methods either prohibit control in deep scenes or require user intervention for focus selection.
Innovation Solution
An imaging apparatus that automatically detects the in-focus area and determines a suitable tilt angle by calculating evaluation values across multiple areas, using a tilt/zoom/focus controller to adjust the image sensor and lens positions based on optimal tilt angles, ensuring a wider depth of field and maintaining focus from short to long distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional surveillance camera is installed with an obliquely downwardly directed optical axis, then the camera can monitor a person passing on a road or capture a car or its license plate, but the focal plane does not coincide with the imaging plane of the object, resulting in out-of-focus areas
Solution Approach 1:
The patent applies dynamics by making the image sensor tiltable relative to the optical axis. The tilting angle is dynamically adjusted based on the detected depth of the object, transforming a static imaging system into a dynamic one that adapts to different depth requirements. This resolves the contradiction by allowing the focal plane to dynamically coincide with the imaging plane for objects at various depths.
Solution Approach 2:
The patent changes the geometric parameter of the image sensor orientation by introducing a tilting angle. This parameter change allows the focal plane to be adjusted to match the imaging plane for objects at different depths, thereby improving focus accuracy while maintaining adaptability to various imaging scenarios.
2Adaptability or versatility
If the Scheimpflug principle is used to expand the depth of field by tilting the optical system or image sensor, then the depth of field is expanded, but it becomes necessary to detect the in-focus area and determine the tilt angle based on evaluation values, increasing system complexity
Solution Approach 1:
The patent applies self-service by enabling the system to automatically detect the in-focus area and determine the optimal tilt angle without requiring external intervention. The evaluation value calculation and tilt angle determination are performed autonomously by the system itself, reducing the need for complex external control mechanisms while maintaining adaptability.
Solution Approach 2:
The patent implements feedback by using evaluation values calculated from the captured image to determine the tilt angle. The system continuously monitors the focus quality through evaluation values and adjusts the tilt angle accordingly, creating a closed-loop control system that simplifies the overall control architecture while achieving adaptive depth of field.
3Reliability
If tilt control is prohibited when mutual coincidence of tilt angles is lower than a predetermined value, then control stability is maintained, but tilt control cannot be applied even in imaging scenes where depth of the object becomes deeper due to tilt imaging
Solution Approach 1:
The patent applies local quality by evaluating the coincidence of tilt angles in different areas independently. Instead of applying a global prohibition based on overall coincidence, the system allows tilt control in specific areas where the coincidence condition is met, while prohibiting it only in areas where it is not met. This localized approach maintains control stability in problematic areas while preserving tilt control applicability in suitable areas.
4Measurement precision
If multiple focus detection areas are used to calculate tilt angles, then focus information can be obtained across different regions, but user intervention is required to specify the target area or select preset modes
Solution Approach 1:
The patent applies self-service by automatically determining which focus detection area to use based on the captured image content and evaluation values. The system autonomously selects the appropriate area without requiring user specification or mode selection, thereby maintaining focus information accuracy while eliminating the need for user intervention.
Solution Approach 2:
The patent implements feedback by using evaluation values from multiple focus detection areas to automatically determine the optimal target area for tilt angle calculation. The system monitors the quality of focus information from different areas and autonomously selects the most suitable one, creating a self-adjusting operation system that maintains precision without requiring user input.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The apparatus effectively maintains an in-focus state across varying depths by detecting the tilt focal plane and determining the optimal tilt angle, allowing for automatic tilt control suitable for each imaging scene, even in complex depth scenarios without user intervention.
Implementation Method 1
an image sensor that tilts around a rotational axis in a horizontal direction or in a vertical direction, or both
Data Source
Figure 1
Figure 2~3B
Figure 4
AI summary
An imaging apparatus includes a controller configured to change a tilt angle between an image sensor and a plane orthogonal to an optical axis of an optical system by adjusting a tilt of the image sensor or the optical system, an evaluation value acquirer configured to acquire contrast evaluation values of a plurality of areas in an image by changing the tilt angle through the controller, and a determiner configured to determine the tilt angle for each of the plurality of areas based on the contrast evaluation values of the plurality of areas acquired by the evaluation value acquirer, and to determine the tilt angle based on the tilt angle of each determined area. The controller adjusts the tilt of the image sensor or the optical system based on the tilt angle determined by the determiner.